In these two tests (and no other tests in jsreftest), we also hit the assertion:
###!!! ASSERTION: Shouldn't ever call this directly!: 'Not Reached', file e:/builds/moz2_slave/mozilla-central-win32-debug/build/dom/plugins/PluginScriptableObjectParent.cpp, line 327
They hit the assertion every time in Windows debug builds, and they also seem to be failing every time.